1. Field of the Disclosure
The technology of this disclosure relates generally to cushioning structures. The cushioning structures can be used for any cushion applications desired, including but not limited to mattresses, seats, foot and back support, and upholstery, as examples.
2. Technical Background
Cushioning structures are employed in support applications. Cushioning structures can be employed in bedding and seating applications, as examples, to provide cushioning and support. Cushioning structures may also be employed in devices for safety applications, such as helmets and automobiles for example.
The design of a cushioning structure may be required to have both high and low stiffness. For example, it may be desirable to provide a cushioning material or device in which a body or object will easily sink into the cushion a given distance before the applied weight is supported. As another example, it may be desired to provide surfaces having low stiffness initially during application of weight, while the underlying structure needs to have high stiffness for support. These surfaces may be provided in safety applications, such as helmets and automobile dashboards as examples. In this regard, a cushioning structure may be designed that provides an initial large deflection at a low applied force with nonlinearly increasing stiffness at increasing deflection.
To provide a cushioning structure with high and low stiffness features, cushioning structures can be composed of layers of varying thicknesses and properties. Each of these components has different physical properties, and as a result of these properties and variations in thicknesses and location of the components, the cushioning structure has a certain complex response to applied pressure. For example, cushioning structures generally include components made from various types of foam, cloth, fibers and/or steel to provide a general response to pressure that is perceived as comfortable to the individual seeking a place to lie, sit, or rest either the body as a whole or portions thereof. General foam plastic materials can also be used as materials of choice for cushion applications. Foam plastic materials provide a level of cushionability in and of themselves, unlike a steel spring or the like structure. Generally accepted foams fall within two categories: thermosets and thermoplastics.
Thermoset materials exhibit the ability to recover after repeated deformations and provide a generally excepted sleep surface. Thermoplastic materials including thermoplastic foams, and specifically closed cell thermoplastic foams, on the other hand, while not having the long time frame repeatable deformation capabilities of the thermoset foams, typically provide greater firmness and support. Further, thermoplastic materials are suitable to lower density, less weight, and therefore less costly production while maintaining a more structurally stable aspect to their construction.
One example of a cushioning structure employing layers of varying thicknesses and properties for discussion purposes is provided in a mattress 10 of FIG. 1. As illustrated therein, a mattress innerspring 12 (also called “innerspring 12”) is provided. The innerspring 12 is comprised of a plurality of traditional coils 14 arranged in an interconnected matrix to form a flexible core structure and support surfaces of the mattress 10. The coils 14 are also connected to each other through interconnection helical wires 16. Upper and lower border wires 18, 20 are attached to upper and lower end turns of the coils 14 at the perimeter of the array to create a frame for the innerspring 12. The upper and lower border wires 18, 20 also create firmness for edge support on the perimeter of the innerspring 12 where an individual may disproportionally place force on the innerspring 12, such as during mounting onto and dismounting from the mattress 10. The innerspring 12 is disposed on top of a box spring 22 to provide base support.
The coils 14 located proximate to an edge 23 of the innerspring 12 are subjected to concentrated loads as opposed to coils 14 located in an interior 24. To provide further perimeter structure and edge support for the innerspring 12, support members 25 may be disposed around the coils 14 proximate to the edge 23 of the innerspring 12 between the box spring 22 and the upper and lower border wires 18, 20. The support members 25 may be extruded from polymer-foam as an example.
To provide a cushioning structure with high and low stiffness features, various layers of sleeping surface or padding material 26 can be disposed on top of the innerspring 12. The padding material 26 provides a cushioning structure for a load placed on the mattress 10. In this regard, the padding material 26 may be made from various types of foam, cloth, fibers and/or steel to provide a generally repeatable comfortable feel to the individual seeking a place to either lie, sit, or rest, either the body as a whole or portions thereof. To provide the cushioning structure with high and low stiffness features, the padding material 26 may consist of multiple layers of materials that may exhibit different physical properties.
For example, foam plastic materials can be used as materials of choice for the padding material 26. Foam plastic materials provide a level of cushionability in and of themselves, unlike a steel spring, or the like structure. For example, an uppermost layer 28 may be a soft layer comprised of a thermoset material. Thus, in the example of FIG. 1, the uppermost layer 28 being provided as a thermoset material allows a load to sink into the mattress 10 while exhibiting the ability to recover after repeated deformations. One or more intermediate layers 30 underneath the uppermost layer 28 may be provided to have greater stiffness than the uppermost layer 28 to provide support and pressure spreading that limits the depth to which a load sinks. For example, the intermediate layers 30 may also include a thermoset material, such as latex as an example. A bottom layer 32 may be provided below the intermediate layers 30 and uppermost layer 28. The uppermost layer 28, the intermediate layers 30, and the bottom layer 32 serve to provide a combination of desired cushioning characteristics. An upholstery 34 is placed around the entire padding material 26, innerspring 12, and box spring 22 to provide a fully assembled mattress 10.
The material selection and thicknesses of the uppermost layer 28, the intermediate layers 30, and the bottom layer 32 of the mattress 10 can be designed to control and provide the desired cushioning characteristics. However, it may be desired to also provide support characteristics in the padding material 26. However, the disposition of layers in the padding material 26 does not easily allow for providing variations in both cushioning and support characteristics. For example, a thermoplastic foam could be included in the padding material 26 to provide greater firmness. However, compression will occur in the thermoplastic foam over time. Regardless, further complications that can occur as a result of including an additional thermoplastic material include the separate manufacturing and stocking for assembly of the mattress 10, thus adding inventory and storage costs. Further, an increase in the number of structures provided in the padding material 26 during assembly of the mattress 10 increases labor costs.